Capacitive sensor with additional noise-registering electrode

ABSTRACT

A capacitive touch sensor employing adjacent drive and sense electrodes, in which an additional sense electrode is provided as well as a conventional drive electrode and sense electrode. The drive and two sense electrodes are arranged on the bottom side of a dielectric panel, the top side providing a sensing surface to be touched by a user&#39;s finger or a stylus. The additional sense electrode is positioned on the underside of the dielectric panel so that it is shielded from the drive electrode by the conventional sense electrode. The signal collected from the additional sense electrode is subtracted from the signal collected from the conventional sense electrode to cancel noise.

RELATED APPLICATION

This application is a U.S. National Stage Filing under 35 U.S.C. 371from International Patent Application Serial No. PCT/GB2008/002816,filed Aug. 20, 2008, and published on Mar. 5, 2009 as WO 2009/027629 A1,which claims the benefit of U.S. Provisional Application Ser. No.60/968,069, filed on Aug. 26, 2007, the content of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The invention relates to capacitive sensors, in particular designapproaches which reduce noise, in particular common mode noise.

Capacitive proximity sensors are based on detecting a disturbance in acapacitive coupling of sensor electrodes, either to ground or to anotherelectrode, caused by the proximity of a pointing object, such as a humanfinger or a stylus.

Example devices include single control buttons, i.e. non-positionsensitive detectors or so-called zero dimensional sensors, as well asposition sensitive detectors which can be classified intoone-dimensional and two-dimensional sensors.

One-dimensional capacitive sensors are found in linear or circular formas lighting controls, television remote controls, and in solid state MP3portable music players, for example.

Two-dimensional capacitive sensors are found in touch screens, touchsensitive keyboards and key pads, for example, and are commonly used inconsumer electronic devices and domestic appliances. Such sensors areoften used in conjunction with an underlying display, such as a liquidcrystal display (LCD), or cathode ray tube (CRT).

Other devices which may incorporate position sensitive capacitivesensors include pen-input tablets and encoders used in machinery forfeedback control purposes, for example. Position sensitive capacitivetouch sensors are capable of reporting at least a 2-dimensionalcoordinate, Cartesian or otherwise, related to the location of an objector human body part, by means of a capacitance sensing mechanism.

Devices employing position sensitive capacitive touch sensors havebecome increasingly popular and common, not only in conjunction withpersonal computers, but also in all manner of other appliances such asland line and mobile telephones, personal digital assistants (PDAs),point of sale (POS) terminals, electronic information and ticketingkiosks, kitchen appliances and the like.

Capacitive touch-sensors can be classified into two types in terms ofthe manner in which the signal is sensed, namely single-ended electrodesand adjacent transverse electrodes.

U.S. Pat. No. 5,730,165 and U.S. Pat. No. 6,466,036 describe acapacitive sensing device of the single-ended electrode type whichrelies on measuring the capacitance of a sensing electrode to a systemreference potential, most commonly earth or ground. The pointing device,typically a human finger or a stylus, thus effectively defines groundand may be thought of as the second “plate” in the capacitor, with thesensing electrode forming the first “plate”. The user's actions may thenbe considered as varying the separation between the plates of acapacitor, and hence vary the measured capacitance.

U.S. Pat. No. 6,452,514 describes a capacitive sensing device of thetransverse electrode type which is based on measuring capacitivecoupling between two adjacent electrodes. In such a sensor, oneelectrode, the so-called drive electrode, is supplied with anoscillating drive signal, and this signal is capacitively coupled toanother electrode, the so-called sense electrode. The degree ofcapacitive coupling of the drive signal to the sense electrode isdetermined by measuring the amount of charge transferred to the senseelectrode by the oscillating drive signal. The amount of chargetransferred, i.e. the strength of the signal seen at the senseelectrode, is a measure of the capacitive coupling between theelectrodes, which is influenced by the proximity of the pointing object.The pointing object therefore may be considered to change the dielectricenvironment, and thus the field, between the two “plates” of thecapacitor formed by the drive and sense electrodes, and hence change themeasured capacitance.

It is known in the art that capacitive touch (or proximity) sensor ofthe transverse electrode type are prone to noise problems, in particularcommon mode noise injected into the raw signal collected during sensing,and the invention aims to solve or mitigate this problem.

SUMMARY OF THE INVENTION

According to the invention there is provided a capacitive touch sensorcomprising a dielectric panel overlying a drive electrode, a first senseelectrode and a second sense electrode, the electrodes being separatedby coupling gaps, wherein the second sense electrode is positioned to beshielded from the drive electrode by the first sense electrode, so thatin use the first sense electrode receives the majority of charge coupledfrom the drive electrode and the second sense electrode primarilyregisters noise.

In this way, the choice of electrode arrangement, in particular theprovision of the second sense electrode which is not normally providedin a conventional capacitive sensor of the transverse electrode type canbe used to reduce noise. This approach contrasts to approaches in whicha conventional electrode arrangement is used, and approaches to reducenoise which are based solely on the signal processing, either by specialdesign of the analogue circuitry used to collect, accumulate and/orprocess the low level signals, or by higher level digital processing.The proposed approach of the invention is not intended to be used to theexclusion of these other techniques, but rather it is preferred that itis used in combination with such other techniques to optimizeperformance. Indeed, it is an advantage of the present invention thatthe approach based on providing an electrode arrangement with a secondsense electrode is compatible with such other techniques for reducingnoise.

Moreover, as will be understood with reference to the detaileddescription, the approach of the invention is applicable to one- andtwo-dimensional capacitive touch sensors, and scalable to provide one-and two-dimensional capacitive touch sensors of different sizes andresolutions as desired.

The sensor preferably further comprises a sensing circuit includingfirst and second detector channels connected to the first and secondsense electrodes to receive first and second signal samplesrespectively, and operable to output a final signal obtained bysubtracting the second signal sample from the first signal sample,thereby to cancel noise. The second sample is subtracted from the firstsample on a sample-by-sample basis, or after summing a plurality ofsamples on each detector channel separately and performing thesubtraction on the summed samples from each detector channel.

The electrodes may advantageously comprise multiple electrode elements,wherein the elements can be connected by suitable conductive wires,lines or traces. The electrode elements of the different electrodes,namely the drive electrode D, and the first and second sense electrodesS0 and S1, can then be interleaved in one or more repeats of thefollowing sequence: . . . D, S0, S1, S0, D, S0, S1 . . . where thesequence preferably starts with either an element of the drive electrodeor the second sense electrode, and preferably terminates with anelectrode element of the same type. Namely, the first sense electrodeand at least one of the drive electrode and the second sense electrodeeach comprise at least two electrode elements, and the electrodeelements are arranged interleaved on the dielectric panel in at leastone repeat of the sequence: drive electrode element, first senseelectrode element, second sense electrode element, first sense electrodeelement, drive electrode element. Or alternatively, the first senseelectrode and at least one of the drive electrode and the second senseelectrode each comprise at least two electrode elements, and theelectrode elements are arranged interleaved on the dielectric panel inat least one repeat of the sequence: second sense electrode element,first sense electrode element, drive electrode element, first senseelectrode element, second sense electrode element. These two sequencesboth provide a symmetrical arrangement whereby the electrode elementscan terminate at both extremities of their repeat pattern either withtwo drive electrodes or two signal sense electrodes.

The invention also provides a method of capacitive touch sensingcomprising: providing a capacitive touch sensor comprising a dielectricpanel overlying a drive electrode, a first sense electrode and a secondsense electrode, the electrodes being separated by coupling gaps,wherein the second sense electrode is positioned to be shielded from thedrive electrode by the first sense electrode; actuating the driveelectrode to couple the majority of charge from the drive electrode tothe first sense electrode; sampling the first sense electrode to collecta first signal sample; sampling the second sense electrode to collect asecond signal sample; subtracting the second signal sample from thefirst signal sample to obtain a final signal; and outputting the finalsignal.

In the method, the said sampling steps are preferably carried outsimultaneously. The invention may also be implemented with the samplingsteps carried out at different times, in particular if the temporalcharacteristics of the noise are predictable.

The inventive concept is also transferable to capacitive sensors of thesingle-ended type to provide further aspects to the invention. Namely,according to a further aspect of the invention there is provided acapacitive touch sensor comprising a dielectric panel overlying ameasurement electrode and a noise electrode separated by a gap, whereinthe measurement electrode is located at an input area and the noiseelectrode is positioned adjacent thereto, so that in use the measurementelectrode receives the majority of charge coupled from a pointing objectand the noise electrode primarily registers noise. There may be multiplemeasurement electrodes, and a noise electrode may be distributed over anarea common to a plurality of the measurement electrodes.

The invention also provides a corresponding method of capacitive touchsensing comprising: providing a capacitive touch sensor comprising adielectric panel overlying a measurement electrode and a noise electrodeseparated by a coupling gap, wherein the measurement electrode islocated at an input area and the noise electrode is positioned adjacentthereto; sampling the measurement electrode to collect a first signalsample; sampling the noise electrode to collect a second signal sample;subtracting the second signal sample from the first signal sample toobtain a final signal; and outputting the final signal.

In the method, the said sampling steps are preferably carried outsimultaneously. The invention may also be implemented with the samplingsteps carried out at different times, in particular if the temporalcharacteristics of the noise are predictable.

It will be appreciated that the invention can be applied to all thetypes of capacitive sensor mentioned in the introduction. Specifically,the invention may be applied to discrete control-buttons,one-dimensional capacitive sensors and two-dimensional sensors with orwithout displays. Moreover, sensors according to the invention may beincorporated in a wide variety of devices including those mentioned inthe introduction.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same maybe carried into effect reference is now made by way of example to theaccompanying drawings.

FIG. 1 shows schematically an electrode configuration of a firstembodiment of the invention.

FIG. 2 shows schematically an electrode configuration of a secondembodiment of the invention.

FIG. 3 shows schematically an electrode configuration of a thirdembodiment of the invention.

FIG. 4 shows schematically an electrode configuration of a fourthembodiment of the invention.

FIG. 5 is a schematic block diagram showing a microcontroller unitsuitable for use in the above embodiments.

FIG. 6 shows schematically an electrode configuration and outputconnections of an alternative embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows schematically an electrode configuration of a firstembodiment of the invention in the form of a basic wheel of the typefamiliar for example from solid state or hard drive MP3 portable musicplayers. This is in effect a linear sensor, known in the art as aslider, wrapped around into a closed circle. It is noted that the sameelectrode configuration could be adapted by notionally cutting it into aC-shape and opening into an arc or line to make a linear or arcuateslider.

The electrode configuration comprises drive electrodes X0, X1, X2, X3provided for respective quadrants of the circle as well as two senseelectrodes Y0 and Y1. The Y0 electrode serves as the conventional senseelectrode of a capacitive touch (or proximity) sensor of the adjacenttransverse electrode type, and the Y1 electrode is an additional senseelectrode provided for noise reference according to the invention. Inthis document, the Y0 electrode is referred to as the signal senseelectrode, and the Y1 electrode as the noise sense electrode.

The principles of a capacitive touch (or proximity) sensor of this typeare described in U.S. Pat. No. 6,452,514 which is incorporated herein byreference. In the case of the present invention, the mode of use is tointerpolate signals between adjacent electrode sets so as to provide amore continuous position sensing effect.

It is noted that the respective surface areas of the Y0 and Y1electrodes are made equal, even though this is not accurately depictedby the schematic drawing which is slightly out of perspective in thisrespect with the Y1 surface area being illustrated as slightly largerthan the sum of the surface areas of the Y0 electrodes. Since the Y0electrode includes two ring elements, and the Y1 electrode only one ringelement, this means that the radial width of the arcuate Y1 electrodeelements is twice that of the Y0 electrode elements. This is done toensure that the Y0 and Y1 electrodes are equivalent for noise.

The sensing element design described herein and shown in the figuressuppresses common mode noise by having two receive or sense electrodesY0 and Y1, which are both adjacent a finger (or other object) touchingor in proximity with an overlying panel surface. Common mode noise iscoupled into the Y electrodes approximately in equal measure, since thefinger will be larger than the width of the electrode set (radially asshown). Signal coupling comes from absorption of coupling from the Xnlines to the Y0 trace arcs (as shown) on edges of the Xn signal's as isusual for a sensor of the transverse electrode type described in U.S.Pat. No. 6,452,514. The Y1 arc electrode does not receive appreciablesignal from lines Xn (X0, X1, X2, X3 electrodes) as it is shielded fromthe Xn arcs by intervening Y0 arcs.

The reader will understand that the various sets of electrodes do notmake direct electrical contact with each other and that appropriatecross-over arrangements that are known in the art are used to providethis isolation. The drive electrodes Xn are shown as sectors orpie-wedges that subtend slightly less than ninety degrees of arc, andthe receive electrodes Yn form nearly complete circles.

FIG. 1 shows that the signals are coupled into the two Y0 arcs from bothan inner and an outer Xn electrode set across the coupling gaps as isknown in the art. The field lines emit from arcs Xn and project into anoverlying dielectric panel, and arc downwards into the Y lines which actas virtual grounds. The Y0 electrode elements receive the majority ofthis charge coupling.

The sensing circuit comprises two sampling detector channels D0, D1connected to electrodes Y0, Y1 respectively, which are sampledrepetitively but in as precise a time-coincidence as is possible, whichis made possible by running these sample channels on the same port of amicrocontroller unit (MCU).

Signal processing comprises the subtraction of the signal samples S0 andS1 (corresponding to detector channels D0, D1) as S_(FINAL)=S0−S1. Thesubtraction can be made either on a sample-by-sample basis or aftersumming a number of samples of S0 and separately a number of samples ofS1 first, e.g.,S _(FINAL) =ΣS0−ΣS1orS _(FINAL)=Σ(S0−S1)

Since signal sample S1 is coupled from electrode Y1 which primarilyregisters noise and very little signal change due to object proximity,and due to dimensional confinement of the electrode set with respect tothe detected object (e.g. a finger), the noise apparent on signal sampleS0 is cancelled by this subtraction process. It is noted that thesurface area of the electrode Y1 should be close to the same electrodearea as electrode Y0, so that the noise coupling is balanced and theprocess of subtraction is efficient at noise reduction.

The additional circuit cost in each case is an extra Y receive line.

The conductive elements may be formed from indium tin oxide (ITO)sensors or copper-based.

Finger location is performed via interpolation among the quadrants as isknown in the art.

The number of X or drive electrodes can be increased proportionate tothe overall diameter for best interpolative effect.

FIG. 2 shows schematically an electrode configuration of a secondembodiment of the invention. Compared with the first embodiment, thesecond embodiment may be characterized by saying that the circle isfilled to allow a Cartesian response without a gap in the middle. FullCartesian readout may be required for example on a track pad. The circleis filled with repeats of the same sequence, e.g., from inside to out:Xn/Y0/Y1/Y0/Xn/Y0/Y1/Y0/Xn

where the first Xn is a filled circle of conductive element in thecentre.

As in the first embodiment, for noise equivalence, the radial width ofthe arcuate Y1 electrode elements is twice that of the Y0 electrodeelements. Similar comments regarding variants as made in relation to thefirst embodiment apply also.

FIG. 3 shows schematically an electrode configuration of a thirdembodiment of the invention. This is topologically identical to theelectrode configuration of the second embodiment, with thecircular/arcuate electrode elements being changed to square shapes.Namely, each of the four drive electrode quadrants is formed of L-shapedelectrode elements, and the four quadrants collectively form a squareshape. The signal and noise sense electrodes are similarly formed ofsquare-shaped elements instead of circular elements.

The conductive sensing pattern can thus be made square, or rectangular,in shape, which may be used for ‘normal’ track pads with Cartesianoutputs. The number of X or drive electrodes can be increasedproportionate to the overall length for best interpolative effect.

FIG. 4 shows a sensor element in the form of a repeating pattern tocreate a Cartesian sensing surface, i.e. two-dimensional touch sensorsurface. This type of electrode pattern may also be used for a linearslider, i.e. one-dimensional touch sensor surface. The number of Xndrive lines can be increased as desired to extend the length and/orhorizontal resolution.

For best interpolative effect, each segment of the drive sensorelectrode Xn should have a length of 8 mm or less.

Additional filtering can and usually should be performed as thedescribed electrode set may not be perfect at noise suppression. As suchthe invention can be seen as one of a number of methods which is usefulin the suppression of noise, often in combination with other methods.

FIG. 5 is a schematic block diagram showing a microcontroller unit (MCU)suitable for use in the above embodiments which comprises a drivecircuit and a sense circuit. The drive electrodes Xn are connected torespective outputs of a drive circuit. The sense circuit is connected toreceive signals from the first and second sense electrodes Y0 and Y1 viathe respective sense channels S0 and S1, and to output the final signalS_(FINAL) to an output thereof. The detailed functioning of the driveand sense circuits will be understood with reference to the prior art,in particular U.S. Pat. No. 6,452,514 referred to above.

While the embodiments show sensors capable of resolving position intwo-dimensions, the invention is equally applicable to one-dimensionalposition sensors as well as capacitive sensors with no position sensingcapability, e.g. discrete buttons.

With reference to the embodiment of FIG. 1, it will be appreciated thata simpler electrode configuration according to the invention could beprovided by omitting the inner two concentric rings of electrodeelements, so that the drive (Xn) electrodes consist only of the singledepicted radially outermost arcuate portion, the signal sense (Y0)electrode consists only of its radially outermost ring portion, and thenoise sense (Y1) electrode is unchanged in its structure. In thisreduced configuration, the Y1 electrode is still screened from the driveelectrodes according to the teaching of the invention. The design can besimplified one stage further by providing only a single drive electrode,in which case the device reduces effectively to a sensor with noposition resolving capability which would be suitable for use as asingle button. Similar variations starting from the other illustratedembodiments can also be envisaged.

With reference to the embodiment of FIG. 1, it will also be appreciatedthat a more involved electrode configuration according to the inventioncould be provided by providing additional outer concentric rings ofelectrode elements following the same sequence.

Providing equal areas for the Y0 and Y1 electrodes for noise equivalenceas described in the embodiments above is not the only design option.Another option is to scale the relative areas of the noise sense andsignal sense electrodes in favor of the signal sense electrodes, i.e. sothat more area is taken up by the signal sense electrodes than the noisesense electrodes, for example in an integer ratio such as 2:1, 3:1, 3:2etc, or an arbitrary ratio. The ratio of Y0/Y1 electrode areas can bedealt with in signal processing by multiplying the magnitude of thesignal from the noise sense electrodes by the inverse of the ratio ofareas between the Y0/Y1 electrodes so that they provide equivalentcontributions. This allows the noise sense electrodes to be made smallerand thus reduce the amount of touch sensor area occupied by the noisesense electrodes, as compared with the signal sense electrodes (anddrive electrodes).

Another approach to the same issue, which may be used instead of or incombination with selection of a desired ratio of areas for the signalsense and noise sense electrodes, is to measure the relativecontribution of the signal sense and noise sense electrodes at acalibration stage, either during manufacture or on device start-up, andto scale the magnitude of the signals received—from the noise senseelectrode according to this calibration.

It will be appreciated that some sources of noise are highly localized,for example noise arising from display drive electronics, when thecapacitive touch sensor overlies a display. In such cases, it isdesirable for the noise sense electrodes to be directly adjacent theircorresponding signal sense electrodes, as in the above embodiments.However, other noise sources may not be localized to the scale of thecapacitive touch sensor, for example many forms of environmental noise,or noise emanating from a separate part of a system of which thecapacitive touch sensor forms a part, for example the noise generated byinternal combustion engine of an automotive vehicle and its effect on acapacitive touch screen in the passenger cabin of the vehicle. In suchcases, the noise sense electrodes may be arranged separate from thesignal sense electrodes, and may indeed not even be located on the areaof the sensor available for touch, but rather around the rim of a touchsensor, for example under a protective frame surrounding the peripheryof the sensor area.

In the above, it was said that the signal and noise detector channels D0and D1 should ideally be sampled simultaneously. While this isdesirable, especially if the noise is spontaneous and asynchronous incharacter, if the noise source is relatively invariant in magnitude overtime, or has a predictable temporal evolution, then the signal and noisedetector channels D0 and D1 may be sampled at different times.

To summarize the above-described embodiments, a capacitive touch sensorof the transverse electrode type is provided. The sensor has anadditional sense electrode as well as the conventional driveelectrode(s) and sense electrode. The drive and sense electrodes arearranged on the bottom side of a dielectric panel, the top sideproviding a sensing surface to be touched by a user's finger or astylus. The additional sense electrode is positioned on the underside ofthe dielectric panel so that it is shielded from the drive electrode bythe conventional sense electrode. As a consequence, the conventionalsense electrode is much more sensitive to the proximity of the finger orstylus than the additional sense electrode which primarily registersnoise. The signal collected from the additional sense electrode is thensubtracted from the signal collected from the conventional senseelectrode, thereby to cancel noise.

FIG. 6 shows schematically an electrode configuration and outputconnections of an alternative embodiment of the invention based on asingle-ended electrode design of the type known from U.S. Pat. No.5,730,165 and U.S. Pat. No. 6,466,036. A conventional array of buttons 1is provided, wherein each button is formed by a measurement electrodearranged on the underside of a dielectric panel (not shown), such as aglass panel, as is well known in the art. Each measurement electrode 1is connected by a suitable conductive connection 3 to a microcontrollerunit (MCU) 5 or other suitable signal processing circuit and in usesupplies a voltage signal V_(K). It will be understood that eachconnection 3 will typically comprise a first portion deposited orotherwise formed on the underside of the panel and a second portion ofexternal wiring to connect to the MCU 5. In the figure, a single row offour electrodes is illustrated, but it will be understood that atwo-dimensional array could be provided, or a single button. It willalso be understood that in many implementations a display, such as anLCD display, will lie on top of or below the sensor array.

According to this embodiment of the invention, there is additionallyprovided a noise electrode 2 which is distributed over an area common tothe measurement electrodes 1, but electrically isolated therefrom bysuitable gaps to avoid short circuiting. Specifically the noiseelectrode 2 is arranged to substantially surround each of themeasurement electrodes 1. In other implementations, the noise electrodecould be only to one side of the measurement electrode, or two sides,for example. The noise electrode 2 is connected to the MCU 5 by aconnection 4 with similar electrical properties to connection 3 and inuse supplies a voltage signal V_(N) to the MCU 5. Similar to theprevious embodiments, signal processing involves the subtraction of thenoise signal samples from the measurement signal samples, i.e. thesignal output from the MCU 5 is, in terms of voltages,V_(FINAL)=V_(K)−V_(N). As in the previous embodiments, the subtractioncan be made either on a sample-by-sample basis or after separatelysumming a number of samples from each electrode first.

The input area provided by the measurement electrodes are preferablyidentifiable by a user, typically visually. This can be achieved in anumber of different ways. For example, the user may identify themeasurement electrode area by a static marking on the panel, such as avisual label, or by surface structure or relief in the panel, such as anindentation or recess, or a promontory or protuberance, or thecombination of both. Alternatively, a display may be used to indicatethe measurement electrode areas. The identification of the input areasto be actuated by the user's finger or other pointing object ensuresthat the measurement electrodes function as such, and the noiseelectrode positioned adjacent thereto receive relatively little signalfrom the pointing object, so that in use the measurement electrodereceives the majority of signal coupled from a pointing object and thenoise electrode primarily registers noise. While this embodiment hasbeen described solely in terms of a single noise electrode this is forsimplicity only. It will be understood that multiple noise electrodesmay be provided, either one for each measurement electrode, or one foreach group of measurement electrodes, for example.

What is claimed is:
 1. A capacitive touch sensor comprising: adielectric panel overlying a drive electrode, a first sense electrodeand a second sense electrode, the electrodes being separated by couplinggaps, wherein the second sense electrode is positioned to be shieldedfrom the drive electrode by the first sense electrode, so that in usethe first sense electrode receives a majority of charge coupled from thedrive electrode and the second sense electrode primarily registersnoise; and a sensing circuit including first and second detectorchannels connected to the first and second sense electrodes to receivefirst and second signal samples, respectively, and operable to output afinal signal obtained by subtracting the second signal sample from thefirst signal sample.
 2. The sensor of claim 1, wherein the second sampleis subtracted from the first sample on a sample-by-sample basis.
 3. Thesensor of claim 1, wherein the second sample is subtracted from thefirst sample after summing a plurality of samples on each detectorchannel separately and performing the subtraction on the summed samplesfrom each detector channel.
 4. The sensor of claim 1, wherein the firstsense electrode and at least one of the drive electrode and the secondsense electrode each comprise at least two electrode elements, and theelectrode elements are arranged interleaved on the dielectric panel inat least one repeat of the sequence: drive electrode element, firstsense electrode element, second sense electrode element, first senseelectrode element, drive electrode element.
 5. The sensor of claim 1,wherein the first sense electrode and at least one of the driveelectrode and the second sense electrode each comprise at least twoelectrode elements, and the electrode elements are arranged interleavedon the dielectric panel in at least one repeat of the sequence: secondsense electrode element, first sense electrode element, drive electrodeelement, first sense electrode element, second sense electrode element.6. A capacitive touch sensor comprising: a dielectric panel overlying aplurality measurement electrodes and a continuous noise electrodedistributed over an area common to the plurality of measurementelectrodes and separated from the plurality of measurement electrodes bya gap, wherein the plurality of measurement electrodes are located atone or more input areas and the continuous noise electrode is positionedadjacent to the plurality of measurement electrodes, so that in use oneor more of the plurality of measurement electrodes receive a majority ofcharge coupled from an object and the continuous noise electrodeprimarily registers noise; and a sensing circuit operable to; receive afirst signal sample from at least one of the plurality of measurementelectrodes; receive a second signal sample from the continuous noiseelectrode; and determine a final signal obtained by subtracting thesecond signal sample from the first signal sample.
 7. The sensor ofclaim 6, wherein the second sample is subtracted from the first sampleon a sample-by-sample basis.
 8. The sensor of claim 6, wherein thesecond sample is subtracted from the first sample after summing aplurality of samples separately and performing the subtraction on thesummed samples.
 9. A capacitive touch sensor, comprising: a dielectricpanel overlying a drive electrode, a first sense electrode and a secondsense electrode, the electrodes being separated by coupling gaps,wherein the second sense electrode is positioned to be shielded from thedrive electrode by the first sense electrode, so that in use the firstsense electrode receives a majority of charge coupled from the driveelectrode and the second sense electrode primarily registers noise;wherein the first sense electrode and at least one of the driveelectrode and the second sense electrode each comprise at least twoelectrode elements, and the electrode elements are arranged interleavedon the dielectric panel in at least one repeat of the sequence: driveelectrode element, first sense electrode element, second sense electrodeelement, first sense electrode element, drive electrode element.
 10. Thesensor of claim 9, further comprising: a sensing circuit including firstand second detector channels connected to the first and second senseelectrodes to receive first and second signal, samples, respectively,and operable to output a final signal obtained by subtracting the secondsignal sample from the first signal sample; wherein the second sample issubtracted from the first sample on a sample-by-sample basis.
 11. Thesensor of claim 9, further comprising: a sensing circuit including firstand second detector channels connected to the first and second senseelectrodes to receive first and second signal samples, respectively, andoperable to output a final signal obtained by subtracting the secondsignal sample from the first signal sample; wherein the second sample issubtracted from the first sample after summing a plurality of samples oneach detector channel separately and performing the subtraction on thesummed samples from each detector channel.
 12. A capacitive touchsensor, comprising: a dielectric panel overlying a drive electrode, afirst sense electrode and a second sense electrode, the electrodes beingseparated by coupling gaps, wherein the second sense electrode ispositioned to be shielded from the drive electrode by the first senseelectrode, so that in use the first sense electrode receives a majorityof charge coupled from the drive electrode and the second senseelectrode primarily registers noise; wherein the first sense electrodeand at least one of the drive electrode and the second sense electrodeeach comprise at least two electrode elements, and the electrodeelements are arranged interleaved on the dielectric panel in at leastone repeat of the sequence: second sense electrode element, first senseelectrode element, drive electrode element, first sense electrodeelement, second sense electrode element.
 13. The sensor of claim 12,further comprising: a sensing circuit including first and seconddetector channels connected to the first and second sense electrodes toreceive first and second signal samples, respectively, and operable tooutput a final signal obtained by subtracting the second signal samplefrom the first signal sample; wherein the second sample is subtractedfrom the first sample on a sample-by-sample basis.
 14. The sensor ofclaim 12, further comprising: a sensing circuit including first andsecond detector channels connected to the first and second senseelectrodes to receive first and second signal samples, respectively, andoperable to output a final signal obtained by subtracting the secondsignal sample from the first signal sample; wherein the second sample issubtracted from the first sample after summing a plurality of samples oneach detector channel separately and performing the subtraction on thesummed samples from each detector channel.